1. Field of the Invention
The present invention relates to an optical apparatus, an optical detector, an optical modulator, an imaging apparatus, and a camera, and more particularly, to an optical apparatus which utilizes surface plasmon.
2. Description of the Related Art
Recently, hole-type optical filters, which have apertures arranged at regular intervals on a metal thin film and perform wavelength selection utilizing surface plasmons, have been proposed in U.S. Pat. No. 5,973,316 and Nature Vol. 424, Aug. 14, 2003 (FIG. 4).
Conventionally, the transmittance of a metal thin film having an aperture diameter equal to or less than a light wavelength is considered to be, as is varied by its film thickness, less than approximately 1%.
However, as described in U.S. Pat. No. 5,973,316, when apertures of a predetermined size are arrayed on a metal thin film at an interval that matches the wavelength of plasmons, the transmittance of light having a wavelength so as to induce surface plasmons is significantly enhanced.
Further, Nature Vol. 424, Aug. 14, 2003 teaches that transmission spectra of RGB may be obtained using this kind of hole-type optical filter utilizing surface plasmons. More specifically, according to the disclosure, transmission spectra having wavelengths of 436 nm (blue), 538 nm (green), and 627 nm (red) were obtained using a metal thin film having subwavelength aperture arrays.
Further, PCT Pamphlet WO 2002/008810 discloses a wavelength filter which utilizes a surface plasmon.